Real simple solution to a leaky new one: Don't buy it.
The new ones don't all leak. I'm sure there's been a Northstar or two that came off the line with a leak.
The problem with the door not opening is the camper wasn't sitting level. Sure signs of a clueless dealer. My door will bind if the box is racked. Works fine in the truck and once it's down on the sawhorses and leveled.
For what the thing is made out of it cannot possibly be rigid.
Why buy new? Because you can get what you want NOW, versus endless months of searching for the exact right camper at the exact right price within driving distance.
Why buy Palomino? Northstars are only available in a few locations around the country. Palomino dealers are all over the place.